A wireless local area network (WLAN) in an infrastructure basic service set (BSS) mode may include an access point (AP) for the BSS and one or more stations (STAs), i.e., wireless transmit/receive units (WTRUs), associated with the AP. The AP may have access to or interface with a Distribution System (DS) or another type of wired/wireless network that may carry traffic in and out of the BSS. Traffic to STAs originating from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic to destinations outside the BSS originating from STAs may be transmitted to the AP to be delivered to the respective destinations. Traffic between STAs within the BSS may also be transmitted through the AP, where the source STA may transmit traffic to the AP, and the AP may deliver the traffic to the destination STA. Such traffic between STAs within a BSS may be referred to as peer-to-peer (P2P) traffic. P2P traffic may also be transmitted directly between the source and destination STAs with a direct link setup (DLS) using an Institute of Electrical and Electronics Engineers (IEEE) 802.11e DLS or an IEEE 802.11z tunneled DLS (TDLS). A WLAN in independent BSS (IBSS) mode may not include an AP, and thus the STAs may communicate directly with each other. This mode of communication may be referred to as an “ad-hoc” mode of communication.
In an IEEE 802.11 infrastructure operation mode, the AP may transmit a beacon on a fixed channel known as the primary channel. The primary channel may be 20 MHz wide and may be the operating channel of the BSS. The primary channel may also be used by the STAs to establish a connection with the AP.
The channel access mechanism in an IEEE 802.11 system may be Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). In this operation mode, every STA, including the AP, may sense the primary channel. If the channel is detected to be busy, the STA may back off. Therefore, only one STA may transmit at any given time in a given BSS.